A Review of Cold hole expansion effect on the fatigue crack growth in welds of a6061-T6 aluminum alloy. Dhanya Prakash RB* and Dr HD Gopalakrishna1 * Associate Professor, ACSCE, Bangalore. 1 Professor, RVCE, Bangalore. Abstract: The cold hole expansion process is a mechanical method to induce compressive residual stresses around circular holes to improve the fatigue life of structural components of aluminum alloys, the material which is used in this paper is purely aerospace and six –zero series is used for welding purpose, in this test 6061-T6 aluminum alloy welded plate with a thickness of 9 mm to analyze the cold hole expansion effect on fatigue crack growth tests conducted in mode I (opening mode) cyclic loading, At R = 0.1, a sharp crack in base metal, weld metal and heat affected zone was propagated from 17 to 24 mm. The residual stress fields due to cold hole expansion were determined with the finite element method. The fatigue crack growth testing was continued up to a crack length of 35 mm (∼ 0.43) at the same R, and crack opening displacements of the post-expansion crack were also determined with the finite element method. This paper reports the experimental results for fatigue crack growth tests in welds of 6061-T6 aluminum alloy (BM (Base Metal), WM (Weld Metal) and HAZ (Heat Affected Zone) before and after the cold hole expansion. In all cases the crack was initiated at the surface of the specimen where the residual stresses were positive. A review taken from few papers in which the cold hole expansion process has been analyzed with the finite element method to determine the residual stresses around the hole Babu et al. (2008) determined that cold expansion technique induced beneficial compressive stresses around circular holes to offset the applied tensile stress resulting in improved fatigue life. De Matos et al. (2005) determined the residual stresses produced by Split Sleeve Cold Expansion (FTI’s) in 2024-T351 aluminum alloy. It was identified that for cyclic loading, the cracks were likely to nucleate on the surface where the residual stresses were positive. Pasta (2012) carried out a numerical simulation in aerospace structures of 6082-T6 aluminum alloy. The results were experimentally validated by means of displacement measurements, with the conclusion that the finite element method was a confident tool to determine residual stress fields introduced by cold hole expansion. Methodology: 1. Materials and welding Plates: Plates of 6061-T6 aluminum alloy with dimensions of 100 mm × 300 mm × 9 mm were welded by means of the modified indirect electric arc (MIEA) welding technique. A basic description of the MIEA technique and joint geometry are shown in Fig. 1aand b. Further details of the MIEA technique have been previously reported in the literature by Ambriz et al. (2009). Fig. 1. (a) Schematic representation of the modified indirect electric arc (MIEA) technique and (b) joint geometry details.